Flow regulating valves are devices that can be adjusted to restrict or increase the flow of a fluid through a conduit. Such valves are generally well known in the art and have many practical applications. For example, in the commercial natural gas production industry, flow-regulating valves are commonly used to vary the flow of natural gas through a network of gas collection pipes. The network of collection pipes often will connect and branch together tens to hundreds of natural gas ground wells in a localized geographic region. The individual wells will feed natural gas through the network of gas collection pipes to a common output location. Often, the desired natural gas output is less than the maximum production capacity of the several wells combined. Such demands can change due to cyclical seasonal trends and for other economic reasons. This creates a need for regulating and monitoring natural gas production from each well to control the supply.
To regulate the production output of each individual well, the branch collection pipe for each individual well typically includes a flow-regulating valve and a gas flow sensor arranged in fluid series. The gas flow sensor indicates the amount of natural gas that flows through the collection pipe. The regulating control valve provides a variable degree of opening that forms a restriction orifice in the collection pipe and thereby sets the natural gas flow rate in the collection pipe.
To adjust the restriction orifice within the collection pipe, the flow-regulating valve is typically a movable/positionable type of valve such as a linearly translatable valve. A valve of this design generally includes a valve body through which a flow passage is disposed. Other components include a plug member located within the flow passage and an elongated valve stem attached to the plug member and that passes through a valve bonnet. The plug member can be linearly translated toward or away from a valve seat within the flow passage between a fully opened position and a fully closed position, and intermediate positions therebetween. The plug member blocks all flow when in the fully closed position and allows for maximum flow when in the fully opened position.
To linearly translate the plug member towards and away from the valve seat, the valve stem can be connected to an actuator typically located adjacent the valve bonnet and which imparts linear translation motion to the valve stem. Accordingly, the valve stem will have to move with respect to the valve housing that it passes into. To prevent the unnecessary loss of process fluids passing through the valve, it is desirable that the intersection between the reciprocating valve stem and the valve bonnet into which the stem passes is well sealed. This is especially desirable where the process fluid is a flammable natural fluid that can potentially produce an explosion or some other poisonous or environmentally harmful process fluid.
One device and sealing method that has been proposed for sealing a linearly moving valve stem is a pressurized seal arrangement of the type taught in, for example, U.S. Pat. No. 6,161,835 to Donald Arbuckle. In pressurized seal arrangements of the type disclosed in Arbuckle, pressure from the process fluid is used to create a dynamic seal preventing leakage from valve stem and pressurizing piston intersection. Specifically, the device uses an intermediary fluid or lubricant onto which the pressure of the flowing process fluid can be imparted. The pressurized intermediary fluid is thereby forced toward the stem thus creating a fluid seal around the stem that prevents leakage of the process fluid to the environment. Additional sealing may be provided by the inclusion of other sealing elements surrounding the stem that are lubricated by the pressurized intermediary fluid. Improvements to tis prior art design are presented herein.